1. Field of the Invention
The present invention relates to a method and to an apparatus for the wireless exchange of items of information between a first station which, in particular is fixed to a missile, and a second station, particularly a stationary station, through the intermediary of a relay station by way of a directionally-optimizable antenna.
2. Discussion of the Prior Art
Such arrangements are known from DE 33 13 648 A1, in such a form that a submunition is moved by means of a carrier into a position over a piece of territory to be reconnoitred and after release from the carrier still uses same as a relay station for the transmission of information to a remote ground station. As the period of time between the missile station (submunition) being released and the relay station (carrier) crashing, due to the system conditions involved, is very short, there are also no long radio distances that have to be bridged across between those two stations. For that reason that publication does not mention any considerations relating to optimisation, in terms of power, of the radio communication or traffic during that short operating period.
For reliable transmission of information, DE 29 10 956 C2 proposes not using a satellite or an aircraft for the relay function, but storing the information to be communicated in a further missile which transmits it towards the ground station again only after launch of the reconnaissance aircraft.
It is generally known from the art of wireless signal transmission that under comparable circumstances the transmission energy requirement is reduced if the radiation characteristic (the so-called lobe) of the transmission antenna is directed with good focussing effect onto the receiving antenna. For suitable antenna tracking between moving systems, it is known at the receiver end to provide for direction-finding in relation to the origin of the received high-frequency energy. For that purpose however the transmitter of the other station must be operating. The expenditure in terms of circuitry and in particular in terms of signal processing circuitry, for direction-finding, with a control parameter which is to be derived therefrom for pivotal movement of the receiving antenna, is very high in comparative terms, in spite of a restricted dynamic, even if the system does not involve mechanical pivotal movement of the antenna but the directional characteristic thereof is electronically pivoted by way of phase-controlled antenna elements (see DE 37 20 173 A1 or GB 2 144 008 A). Therefore tracking of the main antenna lobe, which is derived from such direction-finding, is a failure when dealing with stations which are manoeuvring at very high speed such as for example transmitting or receiving devices on board an aircraft operating at a low height above the ground.
In consideration of those factors the present invention is based on the technical problem of so developing the method and apparatus of the general kind set forth that even a station operating with fast changes in location, in the interests of advantageous radio transmission conditions, operates with antenna tracking which is always at its optimum.